1. Field of The Invention
The present invention relates to a process for producing a thin film magnetic head adapted for use in a magnetic disc device applied as an external storage device of a computer, particularly to a process for forming a so-called write gap separator and a thin film magnetic head produced by means of such a process.
2. Description of the Related Art
A planar type thin film magnetic head as an example of a thin film magnetic head and a process for forming a write gap separator thereof will be described, referring to FIGS. 1A-1C and 2A-2D.
FIG. 1A illustrates a side view of a thin film magnetic head 5 mounted on a slider 1, which flies or floats above the surface of a recording medium 2 when the medium 2 rotates at a high speed. Exchange of magnetic information between the slider 1 and the recording medium 2 to effect so-called read-and-write operation is conducted in this flying state. FIG. 1B illustrates a perspective view of the floating surface of the slider 1, on which a thin film magnetic head 5 is mounted on a rail 3 opposite to the flowing-in tapered end 4 of a pair of rails 3.
FIG. 1C illustrates an enlarged vertical sectional view of the thin film magnetic head 5, in which magnetic poles 7 formed of a looped soft magnetic material having an insulating gap separator 6 on its surface facing the recording medium 2. Coil 8 is formed in an insulating layer combined with the looped soft magnetic material. The magnetic field loop formed within the magnetic poles 7 completes its loop through a magnetic flux leak into the recording medium 2 at the gap 6. A mutual reaction is generated between the electric current flowing in the coil 8, and the magnetic information formed in the recording medium 2 at a location corresponding to the magnetic pole gap 6. Thus, the both operations of magnetic recording and regenerating are achieved.
The process for producing such a thin film magnetic head 5 generally comprises the sequential steps of forming a gap wall 6 and a non-magnetic layer 9 via a so-called scarifying layer on a substrate; then forming an underlayer of the magnetic poles 7; thereafter forming an interlayer insulating layer 10 and a coil layer 8; and finally forming an upper layer of the magnetic poles 7.
FIGS. 2A-2D illustrate a process for forming a gap according to the prior art. After forming a scarifying layer (not shown) on a substrate 11, a plated base layer 13, e.g., of NiFe, a gap layer 14 of a non-magnetic material, e.g., of SiO.sub.2, Ti, etc., and a resist layer 15 are formed in this order (FIG. 2A).
The resist layer 15 is patterned by exposing it to an electron beam, then a narrow resist wall corresponding to the gap is formed, with a width of, e.g., about 0.25 .mu.m (FIG. 2B).
Vertical etching is applied on the gap layer 14, while the patterned resist wall 15' is used as a mask, to form a gap wall 14' and expose the plated base layer 13 (FIG. 2C).
A soft magnetic layer 16 of the magnetic pole material is plated on the substrate having the gap wall 14' and also the exposed plated base layer 13 thereon. Thus, a write gap is completed (FIG. 2D).
As illustrated in FIG. 1C, the lower layer of the magnetic poles 7 approaches the recording medium 2 only at a portion near the gap wall 6, while the lower layer is magnetically insulated from the recording medium 2 via the non-magnetic layer 9 in the other area. Therefore, it is also necessary in practice to have a step of forming a non-magnetic layer 9 in forming the write gap and the magnetic poles. However, such a step is not critical in the present invention and, thus, descriptions of the non-magnetic layer 9 are omitted here and in other portions of the specification.
There are several problems in the above conventional methods of forming a write gap.
First, the electron beam exposure is required to pattern every individual element separately, and thus it requires much more time than the ordinary resist process, in which the entire surface is exposed all at once.
Secondly, the gap width depends on the degree of resolution of resists. It is not possible to obtain a gap width narrower than about 0.25 .mu.m, which is nearly the lowest limit of resist resolution.
Thirdly, a plating process is usually used to form the magnetic pole. However, magnetic materials adapted for use in the plating process are limited.